linux-kernel - [REVIEW][PATCH] pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns

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Message-ID: <87d1bex8mt.fsf_-_@xmission.com>
Date:   Fri, 12 May 2017 12:55:22 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Vovo Yang <vovoy@...gle.com>, Ingo Molnar <mingo@...nel.org>,
        linux-kernel@...r.kernel.org,
        Linux Containers <containers@...ts.linux-foundation.org>
Subject: [REVIEW][PATCH] pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes

Date: Thu, 11 May 2017 18:21:01 -0500

The code can potentially sleep for an indefinite amount of time in
zap_pid_ns_processes triggering the hung task timeout, and increasing
the system average.  This is undesirable.  Sleep with a task state of
TASK_INTERRUPTIBLE instead of TASK_UNINTERRUPTIBLE to remove these
undesirable side effects.

Apparently under heavy load this has been allowing Chrome to trigger
the hung time task timeout error and cause ChromeOS to reboot.

Reported-by: Vovo Yang <vovoy@...gle.com>
Reported-by: Guenter Roeck <linux@...ck-us.net>
Fixes: 6347e9009104 ("pidns: guarantee that the pidns init will be the last pidns process reaped")
Cc: stable@...r.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---

This is what I have queued up posting so it is public knowledge and so
that if anyone can see a flaw it can get fixed.

 kernel/pid_namespace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index de461aa0bf9a..6e51b8820495 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -277,7 +277,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 	 * if reparented.
 	 */
 	for (;;) {
-		set_current_state(TASK_UNINTERRUPTIBLE);
+		set_current_state(TASK_INTERRUPTIBLE);
 		if (pid_ns->nr_hashed == init_pids)
 			break;
 		schedule();
-- 
2.10.1